Short-lived autoimmune-prone mice which develop relatively early in life all of the diseases of aging, e.g., amyloidosis, autoimmunities, vascular diseases, coronary disease, immunodeficiency which renders them susceptible to infection, hyalinizing renal disease associated with high levels of circulating immunocomplexes and immunocomplex injuries, and a high frequency of malignancy, have a genetic fault that may be correctable by cellular engineering. We propose that the life span short-lived autoimmune-prone mice might be greatly prolonged and development of diseases of aging prevented if we can transplant marrow to these short-lived autoimmune-prone mice relatively early in life without producing graft-versus-host reaction (GVHR). This feat would require transplanting marrow to introduce genetically distinct stem cells. The stem cells should come from a strain of mice genetically programmed for long life, and late immunologic disorganization. Such a donor should be resistant to development of autoimmunity, and the marrow transplant should not produce GVHR.